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A rectangular coil $PQ$ has $2n$ turns, an area $2a$ and carries a current $2I,$ (refer figure). The plane of the coil is at $60^o$ to a horizontal uniform magnetic field of flux density $B.$ The torque on the coil due to magnetic force is
A solenoid of $N$ turn, $'l'$ length and $'r'$ radius of cross - section. If current $i$ flow in solenoid then magnetic field at axial mid point will be (where $l\, \simeq \,\,r$ )
A galvanometer coil has a resistance of $12\,\Omega $ and meter shows full scale deftection for a current of $3\,mA$ then to convert it into a voltmeter of range $0\,-18\, V$ a resistance should be added
$A$ microammeter has a resistance of $100\,\Omega$ and $a$ full scale range of $50\,\mu$ $A$. It can be used as a voltmeter or a higher range ammeter provided a resistance is added to it. Pick the correct range and resistance combination $(s)$.
In the circuit diagrams $(A, B, C$ and $D$) shown below, $R$ is a high resistance and $S$ is a resistance of the order of galvanometer resistance $G$. The correct circuit, corresponding to the half deflection method for finding the resistance and figure of merit of the galvanometer, is the circuit labelled as
A current of $0.1\, A$ circulates around a coil of $100$ $turns$ and having a radius equal to $5\, cm$. The magnetic field set up at the centre of the coil is $({\mu _0} = 4\pi \times {10^{ - 7}}\,weber/ampere - metre)$
A galvanometer having a coil resistance of $100\ \Omega$. gives a full scale deflection, when a currect of $I\ mA$ is passed through it. The value of the resistance, which can convert this galvanometer into ammeter giving a full scale deflection for a current of $10\ A$, is :......$Ω$
A proton (mass $m$ and charge $+e$) and an $\alpha -$ particle (mass $4m$ and charge $+2e$) are projected with the same kinetic energy at right angles to the uniform magnetic field. Which one of the following statements will be true